Personal microphone line transformer



July 13, 1965 J. PRESTON 3, 7

PERSONAL MICROPHONE LINE TRANSFORMER Filed Oct. 31, 1960 2 Sheets-Sheet1 INV EN TOR. John Preston July 13, 1965 J. PRESTON 3,194,887

PERSONAL MICROPHONE LINE TRANSFORMER I Filed Oct. 31, 1960 2Sheets-Sheet 2 1''! 1 WR V INVEN TOR. John Preston Attm'm United StatesPatent Ofi 3,1945%? Patented July 13, 1965 ice 3,194,887 PERSONALMICROPHONE LINE TRANSFQRMER .lohn Preston, Trenton, N..l'., assignor toRadio Corporation of America, a corporation of Delaware Filed Oct. 31,1960, Ser. No. 66,022 2 Claims. (Cl. 179-1) The present inventionrelates to microphone systems and more particularly to a system forproviding a personal microphone.

Personal microphones have become popular for use by televisionperformers, since they do not interfere with the performers movementduring a television program. Presently available personal microphoneswhich have the quality of sound pick-up desired in television broadcastapplications are normally worn suspended around the neck of theperformer and are readily visible to the audience. A still smaller,lighter personal microphone is desirable which can be attached to theclothing of the performer, as for example to his necktie, and isessentially unobtrusive. A problem resides in providing personalmicrophones having the size, weight and the quality of sound pick-upwhich are needed for television broad cast applications.

It is, therefore, an object of the present invention to provide animproved microphone system which is small and light in weight, which hashigh quality sound pick-up characteristics, and which is adapted to beworn by a performer.

It is a further object of the present invention to provide an improved,pressure type, dynamic microphone which is small in size and light inweight and which is adapted to be clipped directly to the clothing of aperson using the microphone.

It is a still further object of the present invention to provide animproved microphone as above set forth which is of such size as to beunobtrusive and practically inconspicuous when worn by a user.

It is a still further object of the present invention to provide animproved microphone system wherein noise pick-up is counteracted.

It is another object of the present invention to provide an improvedmicrophone system employing a microphone of the dynamic type smallerthan those of the like type that have been heretofore available withcomparable quality of sound pick-up.

Briefly described, a microphone system in accordance with the inventionincludes a microphone of the pressure responsive type having a vibratingsystem including a voice coil disposed to vibrate in a magnetic field inresponse to sound pressure. The vibrating system and means forgenerating the magnetic field are of extremely small size and areenclosed in a case which may have a clip or otherwise clothing grippingor other engageable element attached thereto. A cable including wireswhich are connected to the voice coil extends from the case. Themicrophone may be clipped to the clothing of a performer, as, forexample, to his necktie, and is of such a small size and weight as notto disturb the arrangement of the performers clothing or freedom ofmovement. The cable is connected to plug means including a transformeras an integral part thereof. This transformer part is interchangeablewith other similar transformer parts to provide a plurality of impedancetransformations. A cable from the plug means extends to an amplifier orother broadcast studio sound equipment.

Because of the construction of the microphone and the provision of plugmeans which includes the interchangeable transformer part, themicrophone itself is of an extremely small size and weight so that theperformer can clip the microphone readily to his necktie, shirt or otherarticle of clothing. This eliminates the need to: suspending themicrophone about the performers neck. The extremely small size of thecase, including the microphone vibrating system, also permits theelimination of a cavity behind the vibrating system which is normallyoccupied by a transformer in known personal microphones. Accordingly,the compliance behind the diaphram which is due to the mass of air inthe case is reduced and the frequency response of the microphone extendsinto the range of high audio frequencies (e.g., from 8,000 to 15,000c.p.s.). The quality of sound pick-up of the microphone system providedby the invention is therefore adequate for broadcast applications.

The invention itself, both as to its organization and method ofoperation, as well as additional objects and advantages thereof, willbecome more readily apparent from a reading of the following descriptionin connection with accompanying drawings, in which:

FIGURE 1 is a pictorial view showing a microphone system provided by theinvention in use by a performer during a broadcast program;

FIGURE 2 is a sectional view of a pressure type dynamic microphone inaccordance with the invention;

FIGURE 3 is a sectional view showing a plug means which is used in amicrophone system provided by the invention; and

FIGURE 4 is a schematic diagram showing the manner in which noisepick-up is reduced in the microphone system provided by the invention.

Referring to FIG. 1, there is shown a broadcast studio in which aperformer 10 is broadcasting a program. A control room 12 is locatedadjacent the studio. This control room 12 contains broadcast audioequipment including studio consoles 14. The consoles include audioamplifiers and preamplifiers. An outlet 16 is provided in the wall ofthe control room 12. This outlet 16 is connected to the input of theaudio amplifiers in the consoles 14. i

The microphone system provided by the invention includes a pressure typedynamic microphone 18 which has a clip or the like 20 attached to thecase thereof. The microphone 18 is clipped to the necktie 24 of theperformer 10 in a manner similar to a conventionl necktie clip. Themicrophone is of such small size and weight as not to disturb the set ofthe performers necktie 24, Alternatively, the microphone 18 may beclipped to the clothing of the performer, as, for example, to his lapel26. The case 22 of the microphone 1'8 and the clip 20 may be painted ina color to match or blend with the clothing of the performer. Since themicrophone 18 is of small size and is attached to the clothing of theperformer, it is unobtrusive. The microphone 18 is connected by means ofa microphone cable 28 to plug means 30. This plug means 30 includes amale plug 32 which is attached to the end of the cable 28 and a case 34having female and male plugs 36 and 38 located, respectively, atopposite ends thereof. The case 34 also contains a transformer for thepurpose of matching the output impedance of the microphone 18 to theinput impedance of the amplifiers in the consoles 14 of the controlroom. The case is interchangeable with other similar cases bydisconnecting the plugs 36 and 38 on one case and connecting the plugs36 and 38 on the other.

The outlet 16 has a receptacle to which a cable 40 is attached. One endof the cable 40 is connected to a female plug 42 which is shownconnected to the male plug 38 of the plug means 3 0.

Plug means 30, including cases containing different transformers, may beincluded in the interchangeable microphone system. Each transformer iscapable of providing a different impedance match. Accordingly, the

output impedance of the microphone 18 can be matched to the inputimpedance of amplifiers in studio consoles which have different inputimpedances. Different broadcast stations and networks use amplifiersystems having different input impedances. Thus, differentmicrophonesystem output impedances are required. For example, the three majorbroadcasting networks in the United States require microphone systemoutput impedances of 30 ohms, 156 ohms, and 250 ohms, respectively. Theoutput impedance of the microphone 1?; alone may be 30 ohms. In theevent that the microphone is used in a broadcast station requiring a 39ohm output impedance,

the male plug 32 of the plug means may be inserted directly into thefemale plug 42 thereof and the case 34 including the transformer may bedisconnected. The plug means 3%) includes different cases 34 withtransformers having different turns ratios between the windings thereofwhich can be used when a 150 ohm or 250 ohm output impedance isreduired. The male and female plugs 32 and 42 of the cables 28 and ltlmay be readily connected to and disconnected from the female plugs 36and male plugs 38 at opposite ends of the different transformer cases34.

The entire plug means 3% may be of very small size. It is desirablyinserted into the coat pocket of the clothing worn by the performer.Alternatively, it may be placed on the floor of the studio.

It will be observed from FIG. 1 that the sound spoken by the performerit) travels along a path substantially such as indicated by the dashedlines-44 to the aperturedcover 46 of the case 22 of the microphone 18.This sound is picked up by the microphone and translated into electricalsignals which pass through the cables 28 and 4'8 and the transformer inthe transformer case 34 to the amplifiers in the studio consoles 14.

A major source of noise in personal microphone systems is attributableto the movement of the performer. In known microphone systems whereinthe microphone is suspended from the neck of the performer, hismovements cause the microphone and cable to rub against his clothing.This rubbing generates undesirable noises which are picked up by themicrophone.

The manner in which noise is generated when the performer moves about isillustrated in FIG. 4. Here, the case 4-8 of a microphone which issuspended from the neck of the performer is shown. This microphone isnormally in contact with a surface 54} of the clothing worn by theperformer. When the performer moves about, the case 48 rubs against thesurface 54 since the microphone swings on the chain or lavalliere whichsuspends it from the neck of the performer. This rubbing generates soundwhich is conducted (1) by way of the case 48 of the microphone, and (2)by way of the air to the diaphgram of the microphone. The dashed lines510 show the direction of transmission, by way of the case 48, of thenoise caused .by rubbing of the case 48 system 5 -iwhich are mounted inthe microphone case 22. The microphone case 22 is generally cup-shapedand may be constructed of aluminum or other non-magnetic material. Theclip Ztl is secured to the case 22 by soldering, welding or in any othersuitable manner. The clip 2% may be a necktie clip, as shown in FIG. 1.Alternatively, the clip 21} may be a spring clip of the type used onfountain pens, or in lieu of the clip, a reversely bent hook or pin maybe used to mount the microphone on the clothing. Accordingly, themicrophone 18 may be clipped in the vest pocket or otherwise to theclothing of the performer as though it were a fountain pen.

The case 22 is terminated by an apertured case cover 46 (FIG. 2) throughwhich the sound spoken by the performer enters the case 22 and exertspressure upon the vibrating system 54.

The magnetic structure 52 includes acup-shaped yoke 56 having along itsouter surface a longitudinal groove 58 which extends generally parallelof the axis of the yoke as. A cylindrical magnet 69 is disposed in theyoke 56. A pole cap 62 of soft magnetic material is disposed on themagnet se. The magnetic end pole caps are held to the yoke 56 by meansofa screw 64 having an axial bore. The yoke has a flange 66 whichengages an internal lip 68 on the case 22s A ring 70 of magneticmaterial provides the top plate of the magnetic structure 52 and definesan air gap with the pole cap 62. A felt washer T2 is disposed betweenthe polecap 62 and the ring 70 and is held in place by means ofapertured rings 74. A terminal block 76 is secured to the base of theyoke 56. It will be noted that the yoke 5'6 and terminal block 76 occupyahncst the entire volume of the case 22, the air space in the case beinglimited.

The vibrating system 54 includes a diaphragm 78, its suspension 80, anda voice coil 82. The suspension is mounted on a ring 84 which isdisposed on top of the yoke 56. The cover 46 engages the top of thesuspension and clamps the vibrating system 54 and magnetic structure 52to the case 22. The wire of the voice coil 82 is brought to terminals76a on the terminal block 76 through the groove 58 in the yoke 56 andthrough a cooperating groove in the ring 84. These grooves arerelatively shallow and do not affect the mechanical strength of thestructure.

against the surface 50 of the clothing. The dashed lines 7 5101 show thedirection of transmission of this noise through the air. 7

It is a feature of the present invention to minimize the generation ofnoise caused by rubbing of the microphone case against the clothing ofthe performer. Since the microphone is of small size and weight, it isclipped to the clothing of the performer. Accordingly, the microphonemoves with the clothing and therefore movement of the case relative tothe clothing, which might cause rubbing and noise, is reduced. Movementof the cable 23 is also minimized since this cable 28 maybe shortbecause the plug means 39, to which the cable 28 is connected, can beinserted in the coat pocket of the performer together with any excesslength of cable. Thus,

noise generated by the rubbing of the cable 28-against the performersclothingis also reduced. 7

Referring to FIG. 2, it will be observed that the microphone 18 includesa magnetic structure 52 and a vibrating The cable '28 extends into thecase 22 through the bottom thereof as viewed in FIG. 2. A sleeve 86 maybe formed in the bottom of the case 22 for firmly holding the cable 28.The wires from the cable 2 8 are connected to the terminals 76a. Themicrophone unit as a whole is very small. For example, the case 22 maybe one inch length along its longitudinal axis and three-quarters inchin diameter. The case is occupied almost entirely by the magneticstructure 52, and the volume confined in back of the diagram 78 isrelatively small as compared with the corresponding volume inconventional microphones, even those of the personal type. Thecompliance of the vibrating system due .to the mass of air in the spacebehind the diaphragm is therefore very low. Accordingly, the frequencyof resonance of the vibrating system is quite high. Thisresonance isclamped by the felt Washer 72. Thus, theresponse of the microphone isregular and extends into the high frequency audio range. The quality ofsound pick-up is therefore adequate for broadcast use of the microphone.

The plug means 363 is shown in detail in FIG. 3. The plug means includesthe male plug 32 to which the cable 28 is connected and the female plug52 to which the cable 46 isconnected. This male plug 32 and this femaleplug 42 may be of known design. The case 34 of the plug means includesthree interconnected, hollow, cylindrical shells 9t 92 and 94. Thefemale plug 36 is disposed in an end shell and the male plug 38 isdisposed in the opposite end shell 94. These plugs 36 and 38 may also beof known construction and will therefore not be described in detailherein. A transformer 96 is disposed in the shell 92, This transformer96 includes a closed E-shaped core structure around the center leg ofwhich primary and secondary windings are located. The primary windingsare connected to the female plug 36. The secondary windings areconnected to the male plug 38. The external surface of the corestructure of the transformer 96 may be coated with insulating materialso that the terminals of the plugs 36 and 38 are not short circuited orotherwise interconnected.

It will be apparent that the male plug 32 may be inserted directly intothe female plug 42 and the transformer unit of the plug means eliminatedif the output impedance of the microphone matches the input impedance ofthe amplifier used by the broadcast studio. In the event that animpedance transformation is required, a different transformer case 34and its associated female and male plugs 36 and 33 may be used, asexplained above.

From the foregoing description, it will be apparent that there has beenprovided an improved dynamic microphone and microphone system. Themicrophone is extremely small in size and weight and may be Worn on theclothing of a performer as a personal microphone with a minimum of noisegeneration and a minimum of conspicuousness. The microphone alsoprovides broadcast quality sound pick-up. The microphone system is alsoessentially universally adaptable for use in different broadcast studiosdespite diiferent input impedances of the studio amplifiers thereof.While only one embodiment of the microphone and microphone systemprovided by the invention has been described, variations in themicrophone and in the microphone system, all within the scope of theinvention, will become apparent to one skilled in the art. Accordingly,the foregoing should be taken as illustrative and not in any limitingsense.

What is claimed is:

1. In a signal translating system, the combination of a microphone forconverting acoustical vibrations into electrical signals capable ofbeing amplified by amplifying means remote from said microphone, a firstcable connected to said microphone for providing a partial output pathfor said signals, a second cable connectable to the input of saidamplifying means and also providing a partial output path for saidsignals, and selectively interchangeable transformer means spaced fromboth said microphone and said amplifying means for connecting saidcables to each other whereby to complete the output path from microphoneand provide a coupling from said microphone to said amplifying means,said transformer means including a casing having a plurality ofdetachably connected shells including a pair of end shells at oppositeends thereof and an intermediate shell, a pair of coupling members, onein each of said end shells, and a transformer in said intermediate shellhaving windings respectively connectable to said coupling members whensaid end shells and said intermediate shells are in connected relation,said first cable being detachably conuectable to one of said couplingmembers and said second cable being detachably connectable to the otherof said coupling members, and said transformer being separable from saidcoupling members upon separation of said end shells and saidintermediate shell to thereby enable ready replacement of saidtransformer at will.

2. A microphone system which comprises a microphone adapted to be wornby a performer and including a case having a clip attached thereto, saidcase being attachable to the clothing of a user by means of said clip,plug means including a transformer unit comprising a casing having apair of end shells and an intermediate shell detachably connected tosaid end shells, a transformer within said intermediate shellinterchangeable Within said plug means upon separation of said end andintermediate shells from each other for providing different impedancetransformations, said transformer unit having a first male plug and afirst female plug respectively within said end shells at opposite endsthereof, said plug means also including a second male plug and a secondfemale plug connectable, respectively, to said first female plug andsaid first male plug of an individual one of said transformer units, anamplifier, a cable connected to said microphone and having one of saidsecond plugs of said plug means at one end thereof, and a second cableconnected to the input of said amplifier at one end thereof and havingthe other of said second plugs at the opposite end thereof.

References Cited by the Examiner UNITED STATES PATENTS 1,574,064 2/26Chamberlain 336-107 1,696,897 1/29 Aiken 179-1 1,741,265 12/29 Wappler336-107 1,991,221 2/35 Kingsford 179-1155 2,176,732 10/39 Faber 179-12,552,800 5/51 Lybarger 179-115 2,611,042 9/52 De Naploi 179-1782,728,818 12/55 Mackey et al 336-142 X 2,862,069 11/58 Marchand et a1 -e179-1155 2,929,877 3/60 Irick 179-1 3,029,307 4/62 Baxt 179-1 X3,052,758 9/62 Berry 179-1 OTHER REFERENCES The Radio-Electronic Master,21st Edition, United Catalog Publishers, Inc., New York, NY. Copyright1956, pages D-3, D-ll, and F-24.

Audio Engineering Society Journal, Vol. 5, No. 2, April 1957, pages83-85.

Electronic Technician, page 55, June 1959.

ROBERT H. ROSE, Primary Examiner.

WILLIAM C. COOPER, L. MILLER ANDRUS,

Examiners.

1. IN A SIGNAL TRANSLATING SYSTEM, THE COMBINATION OF A MICROPHONE FOR CONVERTING ACOUSTICAL VIBRATIONS INTO ELECTRICAL SIGNALS CAPABLE OF BEING AMPLIFIED BY AMPLIFYING MEANS REMOTE FROM SAID MICROPHONE, A FIRST CABLE CONNECTED TO SAID MICROPHONE FOR PROVIDING A PARTIAL OUTPUT PATH FOR SAID SIGNALS, A SECOND CABLE CONNECTABLE TO THE INPUT OF SAID AMPLIFYING MEANS AND ALSO PROVIDING A PARTIAL OUTPUT PATH FOR SAID SIGNALS, AND SELECTIVELY INTERCHANGEABLE TRANSFORMER MEANS SPACED FROM BOTH SAID MICROPHONE AND SAID AMPLIFYING MEANS FOR CONNECTING SAID CABLES TO EACH OTHER WHEREBY TO COMPLETE THE OUTPUT PATH FROM MICROPHONE AND PROVIDE A COUPLING FROM SAID MICROPHONE TO SAID AMPLIFYING MEANS, SAID TRANSFORMER MEANS INCLUDING A CASING HAVING A PLURALITY OF DETACHABLY CONNECTED SHELLS INCLUDING A PAIR OF END SHELLS AT OPPOSITE ENDS THEREOF AND AN INTERMEDIATE SHELL, A PAIR OF COUPLING 